When Did Dinosaurs Live?
Dinosaurs dominated Earth for an incredible 165 million years — far longer than humans have existed.
The Mesozoic Era
Dinosaurs lived during the Mesozoic Era (252-66 million years ago), divided into three periods:
Triassic Period (252-201 million years ago)
The Dawn of Dinosaurs
- First dinosaurs appeared around 230 million years ago
- Early dinosaurs were small, often bipedal
- Shared Earth with other reptiles, early mammals
- Supercontinent Pangaea still intact
Notable dinosaurs: Eoraptor, Coelophysis, Herrerasaurus
Jurassic Period (201-145 million years ago)
The Age of Giants
- Dinosaurs became dominant land animals
- Giant sauropods evolved (Brachiosaurus, Diplodocus)
- First birds (Archaeopteryx)
- Pangaea began splitting
Notable dinosaurs: Stegosaurus, Allosaurus, Brontosaurus, Diplodocus
Cretaceous Period (145-66 million years ago)
Peak Diversity
- Most diverse dinosaur period
- Flowering plants appeared
- T. rex, Triceratops, Velociraptor
- Ended with mass extinction
Notable dinosaurs: Tyrannosaurus rex, Triceratops, Velociraptor, Spinosaurus
For Perspective
- Stegosaurus to T. rex: 80 million years apart (more time than T. rex to us)
- Dinosaur reign: 165 million years
- Humans: ~300,000 years
- Modern humans are closer in time to T. rex than T. rex was to Stegosaurus
The End
66 million years ago, an asteroid impact (plus volcanic activity) triggered mass extinction. All non-bird dinosaurs died.
But birds — living dinosaurs — survived and thrive today.
Related Reading
Listen to the Full Course
Explore prehistory in Dinosaurs: The Complete Guide.